RHEL talks about iSeries, pSeries etc and says to use combinations with
the ALT key.

I don't have an ALT key, and the command and option keys don't work in
its place.

You do the option key is equivalent, on my iBook it's even labeled with

alt.

Perhaps it's just that I'm not far enough in to have alternate vcs.

You may need to use fn to get at the function keys, is this in X or
before hand? If it's in X you'd have to use Ctrl-Option like with
Ctrl-Alt in X.
Try option + fn + F3
I'll confirm on my iMac when I get in.
Paul